Personally I would try and avoid the motorways as best you can...
A) because if its heavy rain, spray makes YOUR visibility less to other drivers....
B) the normal trough's and humps in the surface caused by HGV's makes the M3W a bit skittish.....and the occasional river running across the carriageway a bit scary at 60/70mph....(and if you drop below 60 then your in HGV territory...)
Helmets are difficult to store especially when 2 up....
No additional mechanical problems should occur due to rain, especially when its just been collected from a dealer who one would hope had checked the car over first?
